Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$156.76	5.192%	$164.899	$164.90	$164.90	$164.90
Purchase #2	$187.41	4.618%	$196.0646	$196.06	$196.05	$196.10
Purchase #3	$115.85	6.536%	$123.422	$123.42	$123.40	$123.40
Purchase #4	$19.98	3.542%	$20.6877	$20.69	$20.70	$20.70
Purchase #5	$104.93	12.872%	$118.4366	$118.44	$118.45	$118.40
Purchase #6	$153.67	6.695%	$163.9582	$163.96	$163.95	$164.00
Purchase #7	$115.76	12.404%	$130.1189	$130.12	$130.10	$130.10
7 purchase totals =	$854.36		$917.5870	$917.59	$917.55	$917.60